I personally think your dealer can tell there are vibrations, (those guys really aren't as clueless as we might think
) but they can't figure out why and therefore say there's nothing wrong. If they said they did feel the vibrations and heard the wind noise, but couldn't tell you what was wrong, think about the predicament that would put them in. They'd have to start replacing parts until it was fixed or give you a new car. I bet any outside mechanic or any friend would tell you forthright that they feel vibrations and hear the wind, but they're not liable to fix it, so they can "afford" to be honest.
I had pretty nasty vibrations much like what you describe in my car - albeit mine's older, it's a 99' w/ turbo twist 18's. (at the time the existing tires had about 5k miles on them) Anyways here is what I did and the order I did it:
1. re-balanced all tires at discount tire using their hunter 9700 or something ( the one that does the road force variation, blah, blah, blah stuff). didn't help at all.
2. Got an alignment at a nice shop the BruceLee recommended. Nice shop, quality work, and my car did need some minor adjustments. BUT it didn't solve the vibration issue.
3. took it to the porsche dealership and asked to have the vibrations checked out and also to inspect all suspension/steering/chasis. I think the official verbiage on the invoice was "road test: technician noted normal suspension feed back during road test", and they charged me 50 bones to do the road test. Such BS. At that point i didn't feel there was anything i could do, everything checked out and I felt vibrations are a qualitative observation and that i had no way quantify the vibrations and prove something was wrong.
4. replaced all 4 tires (at this point the tires had 15k miles total on them). I replaced them with Pirelli Pzero's from discount tire. Vibrations gone, completely gone for the last 5k miles.
I basically lived with the vibrations from 5k-15k miles
Maybe you can get the dealer to test drive your car with an extra set of wheels they having lying around? Just a thought.
Good luck,
Larez2